1. Field of the Invention
The present invention relates generally to the field of semiconductor devices. Specifically, the invention relates to semiconductor devices using copper interconnect lines, and methods of manufacturing such semiconductor devices.
2. Description of Related Art
Referring to FIGS. 1a-1e, a known method of manufacturing a known semiconductor device having copper interconnect lines includes the steps of forming a dielectric layer 104 over a semiconductor substrate 102, and etching a plurality of trenches or a plurality of vias 106, or both, into dielectric layer 104. Because copper atoms diffuse readily into other materials, e.g., dielectric materials, such known methods also include the step of forming a barrier layer 110, i.e., a metal barrier layer or a dielectric barrier layer, within trenches or vias 106. For example, known dielectric barrier layers may comprise SiN, SiC, SiCN, or similar dielectric compounds which, when used in a layer of sufficient thickness, substantially reduces or prevents the diffusion of copper atoms from one material to another material. Moreover, known metal barrier layers may comprise Ta, TaN, TiN, or similar metal compounds which, when used in a layer of sufficient thickness, substantially reduces or prevents the diffusion of copper atoms from one material to another material. This method also includes the steps of forming a pure copper seed layer 112 over barrier layer 110 and forming a pure copper plate layer 120 over pure copper seed layer 112. Moreover, a portion of copper seed layer 112, a portion of copper plate layer 120, and a portion of barrier layer 110 subsequently are removed by a known, chemical-mechanical polishing process, and an etch stop layer (not shown) may be formed over exposed copper plate layer 120. The etch stop layer may comprise SiN, SiC, SiCN, or similar dielectric compounds which, when used in a layer of sufficient thickness, substantially reduces or prevents the diffusion of copper atoms from one material to another material.
Nevertheless, many metal compounds have a polycrystalline structure through which atoms readily may diffuse. Consequently, impurities may be added to the known metal barriers in order to decrease the permeability of the metal compound. Although the impurities may allow the known metal barriers to substantially reduce or prevent the diffusion of copper atoms from one material to another material, the impurities increase the resistivity of the metal barrier layer. For example, the resistivity of the metal barrier layer may be ten times greater than the resistivity of the copper layers, which difference degrades the performance of the semiconductor device. With respect to dielectric barrier layers, the dielectric compounds used in known dielectric barrier layers may have an associated dielectric constant between 4.5 and 8.0, which degrades the performance of the semiconductor device. Moreover, the dielectric barrier layer is of a thickness suitable for substantially reducing or preventing copper atoms from diffusing from one material to another material, which further degrades the performance of the semiconductor device.